Java Operator API overview

You use the IBM® Streams Java™ Operator API to implement user-defined operators in Java.

The Javadoc documentation for this API is provided with the Streams installation in the $STREAMS_INSTALL/doc/spl/operator/api/java/api directory. The primary package within this API iscom.ibm.streams.operator. Here is a brief description of its main classes.
  • Operator: This interface defines an operator. The Streams run time calls methods on this interface for initialization and then on for each incoming tuple and punctuation until a shutdown request is made.
  • AbstractOperator: Is an abstract class that developers can extend to implement Operator. It provides a number of useful utility methods.
  • OperatorContext: This interface provides access to the operator's runtime context, including descriptions of the streams and parameters. In addition, it provides access to a Java ScheduledExectorService and ThreadFactory for asynchronous actions.
  • StreamSchema: This interface describes the schema of a port, including the names and types (Java and SPL) of its attributes.
  • StreamingInput: This interface describes an input port, including its schema.
  • StreamingOutput: This interface describes an output port and provides methods to obtain new output tuples and to submit them.
  • Tuple: This interface implements an immutable object that generically represents an incoming tuple.
  • OutputTuple: This interface implements a mutable object that generically represents an outgoing tuple.
The Java Operator API is in the Streams library com.ibm.streams.operator.jar, which is located in $STREAMS_INSTALL/lib. The Java Operator API depends on Apache Commons Math 2.2 library (commons-math-2.2.jar) which is located in $STREAMS_INSTALL/ext/lib. When you develop Java operators using the Java Operator API, the com.ibm.streams.operator.jar and commons-math-2.2.jar libraries are required in the class path or build environment. Sample operators and patterns, including source, are supplied in the Streams library com.ibm.streams.operator.samples.jar, which is in $STREAMS_INSTALL/lib.
Note: All of these libraries are automatically added by the Streams run time for operator invocation, thus they must not be declared as dependencies of a Java primitive operator or included in the classLibrary parameter for a JavaOp invocation.

The Streams run time provides a Java SE Version 8 execution environment for operators that are implemented using the Streams Java Operator API. The virtual machine that is used by a stream processing application is defined by the setting of the environment variable JAVA_HOME when the SPL compiler (sc) is run.